While many are able to spend their nights sleeping soundly, 15 percent of Americans, and by some accounts even more, find this simple state of altered consciousness vexingly evasive. For some, a lack of slumber can be so chronic that it hinders memory, concentration and overall well-being.

But why can some people snooze the hours away blissfully while others are wide awake in bed rehashing conversations in their heads, worrying about money, going over the lyrics of classic rock songs and fretting over their to-do lists?

A clue to the answer may have been uncovered in new research from Johns Hopkins University School of Medicine and published in the journal Sleep.

Assistant professor of neurology Dr. Rachel Salas and her colleagues undertook research that included 18 insomniacs and 10 healthy sleepers. In their study they employed transcranial magnetic stimulation (TMS) to measure brain plasticity, or the brain's ability to adapt and change.

"The more plastic your brain, the better it's able to adapt to new memories and new learning or an event like a stroke," Salas explained. "It's usually a good thing. You want your brain to be able to adapt and change to keep up with what you need it to do."

The expectation was that the brains of those who slept poorly would be less plastic during waking hours, but when brain activity was tracked, they found that the brains of insomniacs were busier than those of the normal sleepers.

"It's like they're constantly on, constantly being activated," Salas said. The findings confirm the complaints of many an insomniac: their brains run on warp speed and won’t calm down.

Other studies have shown that the brains of insomniacs are bustling all day and continue to rev even when they’re supposed to be recharging at night.

“There is a theory out there, it’s called hyperarousal, and essentially in basic terms we believe the light switch is always on. And it’s not just nighttime, so insomnia disorder has now become a 24/7 disorder,” Salas said in an interview.

“These patients tend to have higher metabolism rates, even their EEG's, their brain-wave frequencies, are faster when they’re supposed to be asleep.”

And now that Salas and company have shown that insomniac brains suffer from over-excitement, the hope is that it might lead to new studies targeting hyperarousal as a potential treatment.

Until then it may seem that there is no rest for the weary, but there are things that can help lull a hyper brain to sleep. Some people swear by the Chinese mediation practice of qigong; and there are a host of other home remedies to quell that which keeps you up at night as well.